If you get past the basic and advanced SEO tests, you'll get access to how to have a real keyword research tool, as everything paid or free on the market is missing most of the data. So while its just as bad as the rest, this one at least is free for people to use:
For your own sites, you can get all the keyword data directly from Google, here:
https://search.google.com/search-console/performance/search-analytics
Once you have some keywords you want to know more about thier potential demand, using the historical keyword data from Google is your baseline here:
https://ads.google.com/aw/keywordplanner/home
Perfect for comparing 2 keyword patterns to see what is better, for example you can test singular vs plural or split vs combined words and quickly know which is the better keyword.
https://trends.google.com/trends/